Method for de-spreading quadrature pseudorandom noise

ABSTRACT

The present invention discloses a method for de-spreading quadrature pseudorandom noise, which including: inputting data sequences I′ and Q′, and inputting pseudorandom noise sequences PNI and PNQ, on which quadrature pseudorandom noise de-spreading operation will be performed; in each timeslot, extracting continuously 2048 codeword from each pseudorandom noise sequence PNI and each pseudorandom noise sequence PNQ respectively, performing time-division de-multiplexing operation on the 2048 codeword respectively, and obtaining pseudorandom noise sequences PNI′ and PNQ′ both with a length of 1600 codeword; performing quadrature pseudorandom noise de-spreading operation on the pseudorandom noise sequences PNI′ and PNQ′ and the data sequences I′ and Q′ with a length of 1600 codeword input in the timeslot, and then outputting data sequences I and Q. The invention operates the input sequences to be performed with quadrature PN de-spreading. Thereby, system transmission requirement is satisfied, and complexity of transmitting end is relatively lowered.

FIELD OF THE INVENTION

The present invention relates to enhanced broadcast-multicast service inCDMA (Code Division Multiple Access) wireless communication systems,particularly, to a method for de-spreading quadrature pseudorandomnoise.

BACKGROUND OF THE INVENTION

The 3rd Generation mobile communication system (IMT-2000) and theevolved system thereof, i.e. future mobile communication system, aredesigned to be an advanced mobile communication system capable ofovercoming the main disadvantage of the first Generation and 2ndGeneration mobile communication system thoroughly. An outstandingfeature of the 3rd Generation communication system is to enable apersonal terminal user to realize high-quality mobile communication andtransmission of any information, with any person, in any way, at anytime and at any place in the worldwide, in the future mobilecommunication system.

The 3rd Generation mobile communication system mainly consists ofTD-SCDMA formulated by China, CDMA2000 formulated by the U.S.A. andWCDMA formulated by Europe. CDMA2000 Standard is widely used in NorthAmerica and many other places around the world, and in order to furtherimprove the CDMA2000 Standard, the evolved standards of CDMA2000 havebeen formulated: CDMA2000 EV/DO and CDMA2000 EV/DV.

In EV/DO system, EBCMCS (Enhanced BroadCast MultiCast Service) isproposed, and the EBCMCS system is mainly used to transmit broadcastmessage to mobile stations in a whole coverage area. The architecture ofEBCMCS channel is illustrated in FIG. 1: firstly, perform channel codingon the data information input, while the channel coding is ⅕ or ⅓ Turbocoding 101, then, perform channel scrambling, interleaving, repeatingand punching 102 on the data been coded, dividing the coded data intotwo ways of I and Q through 16 QAM (quadrature Amplitude Modulation)103, and perform OFDM (Orthogonal Frequency Division Multiplexing)modulating process on the two ways of I and Q respectively, then thedata passes through quadrature PN (Pseudo-random Noise) de-spreadingmodule 108, and perform time-division multiplexing on the data and pilotand MAC (Media Access Control) information, as shown in FIG. 2, andfinally, sending the data through quadrature PN spreading module 203with Base Station (BS for short) information. Wherein, the OFDMmodulation module comprises mainly: inserting guard interval and pilotmodule 104, QPSK (quadrature Phase Shift Keying) spreading module 105,IFFT (Inverse Fast Fourier Transform) module 106, and inserting cyclicprefix module 107. Wherein, the QPSK spreading module 105 mainlyfunctions to reduce the Peak-to-Average Ratio of OFDM.

In EBCMCS, to make it convenient for the mobile station to demodulatebroadcast information, in the previous downlink, information about theBS, which is added to the sending sequence through the quadrature PNspreading module, needs to be shielded. Therefore, before each timeslotis generated, a quadrature PN de-spreading module needs to be added, andas shown in FIG. 1 and FIG. 2, perform quadrature PN de-spreadingprocessing to the data information input, and then input the datainformation to the TDM (Time Division Multiplexing) module and performtime-division multiplexing with Pilot Channel and MAC information, andfinally, add a BS identifier through the quadrature PN spreading module,to form and send a complete timeslot. The simplified block diagram ofthe whole transmitting end is shown in FIG. 2.

The quadrature PN spreading mode is explained in the EBCMCS Protocol(3GPP2 C.S0054-A Version 1.0 cdma2000 High Rate Broadcast MulticastPacket Data Air Interface Specification of 3GPP2). deep research on thequadrature PN de-spreading mode has been made, and a new quadrature PNde-spreading mode is proposed in this application.

SUMMARY OF THE INVENTION

The present invention mainly aims to provide a method for de-spreadingquadrature pseudorandom noise, to lower complexity of a transmittingend.

To realize the object, according to the first aspect of the invention, amethod for de-spreading quadrature pseudorandom noise is provided,including the following steps:

S102, inputting data sequences I′ and Q′, and inputting pseudorandomnoise sequences PNI and PNQ, on which quadrature PN de-spreadingoperation will be performed;

S104, in each timeslot, extracting continuously 2048 codeword from eachpseudorandom noise sequence PNI and each pseudorandom noise sequence PNQrespectively, performing time-division de-multiplexing operation on the2048 codeword respectively, and obtaining pseudorandom noise sequencesPNI′ and PNQ′ both with a length of 1600 codeword; and

S106, performing quadrature pseudorandom noise de-spreading operation onthe pseudorandom noise sequences PNI′ and PNQ′ and the data sequences I′and Q′ with a length of 1600 codeword input in the timeslot, and thenoutputting data sequences I and Q.

The pseudorandom noise sequences PNI and PNQ both with 32768 codeword,extracting 2048 codeword in each timeslot respectively, and extractinganother immediate following 2048 codeword in sequence from the nexttimeslot; after the whole pseudorandom noise sequence has beenextracted, starts extraction again from the beginning, and theextraction is circled every other 16 timeslots.

The pseudorandom noise sequences PNI and PNQ are respectively generatedby the following multinomials:PI(x)=x ¹⁵ +x ¹³ +x ⁹ +x ⁸ +x ⁷ +x ⁵+1,PQ(X)=x ¹⁵ +x ¹² +x ¹¹ +x ¹⁰ +x ⁶ +x ⁵ +x ⁴ +x ³+1,Wherein, when fourteen “0” appears continuously, one “0” will be addedautomatically.

Calculation formula for the quadrature PN de-spreading operation is:I=½(I′PNI′+Q′PNQ′), and Q=½(Q′PNI′−I′PNQ′).

The pseudorandom noise sequences PNI and PNQ are sequences which consistof

$\pm {\frac{1}{\sqrt{2}}.}$The calculation formula for quadrature PN de-spreading operation is:

${I = {\frac{1}{\sqrt{2}}\left( {{I^{\prime}{PNI}^{\prime}} + {Q^{\prime}{PNQ}^{\prime}}} \right)}},{and}$$Q = {\frac{1}{\sqrt{2}}{\left( {{Q^{\prime}{PNI}^{\prime}} - {I^{\prime}{PNQ}^{\prime}}} \right).}}$

After S106, time-division multiplexing and quadrature PN spreading areperformed on the data sequences I and Q; and then sending the datasequences I and Q. Time-division multiplexing is performed on the datasequences I and Q with pilot and MAC information. The pseudorandom noisesequences PNI and PNQ is adopted in the qauadrature pseudorandom noisespreading.

The quadrature PN de-spreading method is applicable to EnhancedBroadCast MultiCast Service.

To realize the above objective, according to the second aspect of theinvention, a broadcast method for Enhanced BroadCast MultiCast Serviceis provided, including the following steps:

S202, performing channel coding, channel scrambling, interleaving,repeating and punching, 16 QAM, OFDM (orthogonal frequency divisionmultiplexing), on data flow input from physical layer, and generatingdata sequences I′ and Q′

S204, performing quadrature pseudorandom noise de-spreading on the datasequences I′ and Q′ by the method for de-spreading quadrature PNaccording to above, and outputting data sequences I and Q; and

S206, performing time-division multiplexing on the data sequences I andQ with pilot and MAC information, adding base station informationthrough quadrature PN spreading, and transmitting broadcast andmulticast data thereby.

With above technical solution, operations can be performed on the inputsequences on which quadrature PN de-spreading will be performed.Thereby, system transmission requirement is satisfied, and complexity ofa transmitting end is relatively lowered.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings intend to help further understanding of theinvention, and constitute part of the application. The illustrativeembodiments of the invention and their description are used to explainthe invention, and shall not be construed as improper limitations on theinvention. In the appended drawings:

FIG. 1 is a schematic view of EBCMCS Channel architecture;

FIG. 2 is a simplified block diagram of EBCMCS transmitting end;

FIG. 3 is a flow chart of the method for de-spreading quadraturepseudo-random noise according to the present invention;

FIG. 4 is a schematic chart of realizing quadrature PN de-spreadingaccording to the embodiment of the invention;

FIG. 5 is a schematic chart of TDM mode according to the embodiment ofthe invention;

FIG. 6 is an illustrative chart of using mode of short PN sequenceaccording to the embodiment of the invention; and

FIG. 7 is a block diagram of quadrature PN spreading according to theembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in details withreference to the appended drawings, is to be given below. Wherein, ifnot conflict, the embodiments and the technical features of theembodiments can be combined.

Referring to FIG. 3, the method for de-spreading quadrature PN accordingto the present invention includes the following steps:

S102, inputting data sequences I′ and Q′, and inputting pseudorandomnoise sequences PNI and PNQ, on which a quadrature PN de-spreadingoperation will be performed;

S104, in each timeslot, extracting continuously 2048 codeword from eachpseudorandom noise sequence PNI and each pseudorandom noise sequence PNQrespectively, performing time-division de-multiplexing operation on the2048 codeword respectively, and obtaining pseudorandom noise sequencesPNI′ and PNQ′ both with a length of 1600 codeword; and

S106, performing quadrature pseudorandom noise de-spreading operation onthe pseudorandom noise sequences PNI′ and PNQ′ and the data sequences I′and Q′ with a length of 1600 codeword input in the timeslot, and thenoutputting data sequences I and Q.

The pseudorandom noise sequences PNI and PNQ both with 32768 codeword,extracting 2048 codeword in each timeslot respectively, and extractinganother immediate following 2048 codeword in sequence from the nexttimeslot; after the whole pseudorandom noise sequence has beenextracted, starts extraction again from the beginning, and theextraction is circled every other 16 timeslots.

Pseudorandom noise sequences PNI and PNQ are respectively generated bythe following multinomials:PI(x)=x ¹⁵ +x ¹³ +x ⁹ +x ⁸ +x ⁷ +x ⁵+1, andPQ(X)=x ¹⁵ +x ¹² +x ¹¹ +x ¹⁰ +x ⁶ +x ⁵ +x ⁴ +x ³+1,Wherein, when fourteen “0” appears continuously, one “0” will be addedautomatically.

The calculation formula for quadrature PN de-spreading operation is:I=½(I′PNI′+Q′PNQ′), and Q=½(Q′PNI′−I′PNQ′).Pseudorandom noise sequences PNI and PNQ consist of

$\pm {\frac{1}{\sqrt{2}}.}$The calculation formula for quadrature PN de-spreading operation is:

${I = {\frac{1}{\sqrt{2}}\left( {{I^{\prime}{PNI}^{\prime}} + {Q^{\prime}{PNQ}^{\prime}}} \right)}},{and}$$Q = {\frac{1}{\sqrt{2}}{\left( {{Q^{\prime}{PNI}^{\prime}} - {I^{\prime}{PNQ}^{\prime}}} \right).}}$

After S106, time-division multiplexing and quadrature PN spreading areperformed on data sequences I and Q which will be sent then.Time-division multiplexing is performed on data sequences I and Q withpilot and MAC information. The pseudorandom noise sequences PNI and PNQare adopted in the qauadrature pseudorandom noise spreading.

The quadrature PN de-spreading method is applicable to EnhancedBroadCast MultiCast Service.

The broadcast method for EBCMCS according to the present inventioncomprises the following steps:

S202, performing channel coding, channel scrambling, interleaving,repeating and punching, 16 QAM, OFDM, on data flow input from physicallayer, and generating data sequences I′ and Q′;

S204, performing quadrature PN de-spreading on data sequences I′ and Q′according to the method for de-spreading quadrature PN as shown in FIG.3, and outputting data sequences I and Q; and

S206, performing time-division multiplexing on the data sequences I andQ with pilot and MAC information, adding base station informationthrough quadrature PN spreading, and transmitting broadcast andmulticast data thereby.

The invention relates to the part of Air Interface in CDMA (CodeDivision Multiple Access) communication field, in particular to the partof Air Interface involved in Enhanced BroadCast MultiCast Service.

The invention proposes a new quadrature PN de-spreading mode whichcompletes the whole quadrature PN de-spreading function by processingthe two ways of input PN sequences I and Q. The mode is easy to berealized and is less complex than processing the input data sequences.FIG. 4 illustrates the block diagram for realizing the mode.

1) Suppose I′ and Q′ are input data, PN_(I) and PN_(Q) are respectivelytwo ways of PN sequences I and Q to be performed with quadrature PNde-spreading operation.

2) In a timeslot, 2048 codeword are extracted continuously from a shortPN sequence with a length of 32768 codeword, to perform operation.However, to shield the effect of the quadrature PN spreading, it is notjust simply to continuously extract 2048 codeword when the quadrature PNde-spreading is performed. As the length of data sequences input in eachtimeslot is not 2048 codeword but 1600 codeword (the length is onlyextended to 2048 codeword after TDM). Therefore, only 1600 codeword canbe extracted from the 2048 codeword of the sequence to be performed withquadrature PN spreading for quadrature PN de-spreading operation,according to the time-division de-multiplexing principle.

3) Therefore, first let the 2048 codeword of the input PN_(I) and PN_(Q)pass through the time-division de-multiplexing module, and thetime-division de-multiplexing principle is determined according to FIG.4, and then the quadrature PN de-spreading operation shown in FIG. 4 isperformed on the extracted 1600 codeword, to obtain data sequences I andQ.

4) Perform TDM and quadrature PN spreading operation on data sequences Iand Q which are then sent.

5) The basic principle of the method proposed herein lies in processingthe input sequences PN_(I) and PN_(Q) to be performed with quadrature PNde-spreading to satisfy transmission requirement of the system and lowerthe complexity of the transmitting end, instead of processing data tosatisfy transmission requirement.

Referring to FIG. 4, the quadrature PN de-spreading is to be describedin details:

1) Describe the short-code PN sequences involved in the quadrature PNde-spreading. According to the EBCMCS protocol, the two ways of short PNsequences I and Q are respectively generated by the following twomultinomials:P _(I)(x)=x ¹⁵ +x ¹³ +x ⁹ +x ⁸ +x ⁷ +x ⁵+1  (1)P _(Q)(x)=x ¹⁵ +x ¹² +x ¹¹ +x ¹⁰ +x ⁶ +x ⁵ +x ⁴ x ³+1  (2)

According to (1) and (2), the length of the short-code PN sequenceshould have been 2¹⁵−1, but it is specified in the protocol that whenfourteen “0” appears continuously, one “0” will be added automatically,so the length of the short PN sequence becomes 2¹⁵=32768.

2) The use of the short PN sequence is continuous, as shown in FIG. 6.The 1^(st) to the 2048^(th) codeword of the short PN sequence areextracted when the first timeslot is transmitted; the 2049^(th) to the4096^(th) codeword are extracted when the second timeslot istransmitted; extraction is conducted in turn, and after one whole shortPN sequence has been extracted, extraction is started from the 1^(st)codeword cyclically. Since the length of the short PN sequence is 32768codeword, 16 times the length of 2048 codeword, the short PN sequencewill be cyclically extracted for a round every other 16 timeslots.

3) According to the EBCMCS protocol, the calculation formula forquadrature PN spreading is expressed by the following two formulas:I′=IPN _(I) −QPN _(Q)  (3)Q′=IPN _(Q) +QPN _(I)  (4)

According to formulas (3) and (4), FIG. 7 can be used to show the blockdiagram of the quadrature PN spreading,

wherein, I and Q are input sequences to be performed with quadrature PNspreading, while I′ and Q′ are output sequences having been performedwith quadrature PN spreading. According to the downlink channelarchitecture specified in the EBCMCS protocol, I and Q both have 2048codeword for one timeslot. PN_(I) and PN_(Q) are respectively two waysof PN sequences I and Q to be performed with quadrature PN spreading,and PN_(I) and PN_(Q) are extracted according to the principle in 2).

4) According to calculation formulas (3) and (4) of quadrature PNspreading, the formulas of quadrature PN de-spreading can be deduced asshown in the following formulas:I=½(I′PN _(I) +Q′PN _(Q))  (5)Q=½(Q′PN _(I) −I′PN _(Q))  (6)

Wherein, I and Q are input sequences having performed with quadrature PNde-spreading, I′ and Q′ are output sequences to be performed withquadrature PN de-spreading. PN_(I) and PN_(Q) are respectively two waysof PN sequences I and Q to be performed with quadrature PN de-spreading,and PN_(I) and PN_(Q) are extracted according to the principle in 2).Herein, in one timeslot, PN_(I) and PN_(Q) are respectively the same asPN_(I) and PN_(Q) of quadrature PN spreading.

5) As the EBCMCS protocol rules that the time-division multiplexingmodule follows the quadrature PN de-spreading module, as shown in FIG.2, the length of the two ways of data sequences I and Q in each timeslotentering the quadrature PN de-spreading module is 1600 codeword.Therefore, formulas (5) and (6) may be rewritten as:I=½(I′PN′ _(I) +Q′PN′ _(Q))  (7)Q=½(Q′PN′ _(I) −I′PN′ _(Q))  (8)Wherein, PN′_(I) and PN′_(Q) are two ways of short PN sequences I and Q,after performing time division de-multiplexing on PN_(I) and PN_(Q). Thetime-division de-multiplexing principle is determined by the inverseprocess according to FIG. 5. I′ and Q′ are input data sequences to beoperated. We may deduce that sequences I′ and Q′ have a length of 1600codeword for each timeslot, for the current sequences have not gonethrough the time-division multiplexing module. Thus, the block diagramof the overall operation can be shown as FIG. 4.

6) As the EBCMCS Protocol specifies that sequences PN_(I) and PN_(Q)consist of

$\pm {\frac{1}{\sqrt{2}}.}$(7) and (8) may be rewritten as:

$\begin{matrix}{I = {\frac{1}{\sqrt{2}}\left( {{I^{\prime}{PNI}_{I}^{\prime}} + {Q^{\prime}{PN}_{Q}^{\prime}}} \right)}} & (9) \\{Q = {\frac{1}{\sqrt{2}}\left( {{Q^{\prime}{PNI}_{I}^{\prime}} - {I^{\prime}{PN}_{Q}^{\prime}}} \right)}} & (10)\end{matrix}$

7) According to the above principles, the mode for realizing the overallquadrature PN de-spreading can be illustrated in FIG. 4.

According to the embodiment of the present invention, computer programproduct for intra-system handoff is also provided. The computer programproduct comprises instructions for causing a processor to perform thesteps shown in FIG. 3. For the person skilled in the art, it is easy tobe achieved by referring to the embodiments described above and thefigures, so details will be omitted.

The present invention has been shown with reference to theabove-described embodiments thereof, and it is not to be limited by theabove embodiments. It should be understood by those skilled in the artthat various alterations and changes may be made within the spirit andscope of the invention. All modifications, equivalent substitutions orimprovement made therein is intended to be embraced in the claims ofthis invention.

1. A method for de-spreading quadrature pseudorandom noise, comprising:inputting data sequences I′ and Q′, and inputting pseudorandom noisesequences PN_(I) and PN_(Q), on which quadrature pseudorandom noisede-spreading operation will be performed; in each timeslot, extractingcontinuously 2048 codeword from each pseudorandom noise sequence PN_(I)and each pseudorandom noise sequence PN_(Q) respectively, performingtime-division de-multiplexing operation on the 2048 codewordrespectively, and obtaining pseudorandom noise sequences PN_(I)′ andPN_(Q)′ both with a length of 1600 codeword; and performing quadraturepseudorandom noise de-spreading operation on the pseudorandom noisesequences PN_(I)′ and PN_(Q)′ and the data sequences I′ and Q′ with alength of 1600 codeword input in the timeslot, and then outputting datasequences I and Q, wherein subsequent time-division multiplexing andquadrature pseudorandom noise spreading are performed on the datasequences I and Q before the data sequences I and Q are sent.
 2. Themethod for de-spreading quadrature pseudorandom noise according to claim1, wherein the pseudorandom noise sequences PN_(I) and PN_(Q) both with32768 codeword, extracting 2048 codeword in each timeslot respectively,and extracting another immediate following 2048 codeword in sequencefrom the next timeslot; after the whole pseudorandom noise sequence hasbeen extracted, starts extraction again from the beginning, and theextraction is circled every other 16 timeslots.
 3. The method forde-spreading quadrature pseudorandom noise according to claim 2, whereinthe pseudorandom noise sequences PN_(I) and PN_(Q) are respectivelygenerated by the following multinomial:P _(I)(x)=x ¹⁵ +x ¹³ +x ⁹ +x ⁸ +x ⁷ +x ⁵+1,P _(Q)(x)=x ¹⁵ +x ¹² +x ¹¹ +x ¹⁰ +x ⁶ +x ⁵ +x ⁴ +x ³+1 wherein, whenfourteen “0” appears continuously, one “0” will be added automatically.4. The method for de-spreading quadrature pseudorandom noise accordingto claim wherein the calculation formula for the quadrature pseudorandomnoise de-spreading operation is:${I = {\frac{1}{\sqrt{2}}\left( {{I^{\prime}{PNI}^{\prime}} + {Q^{\prime}{PNQ}^{\prime}}} \right)}},{Q = {\frac{1}{\sqrt{2}}{\left( {{Q^{\prime}{PNI}^{\prime}} - {I^{\prime}{PNQ}^{\prime}}} \right).}}}$5. The method for de-spreading quadrature pseudorandom noise accordingto claim 1, wherein the pseudorandom noise sequences PN_(I) and PN_(Q)are sequences which consist of $\pm {\frac{1}{\sqrt{2}}.}$
 6. The methodfor de-spreading quadrature pseudorandom noise according to claim 5,wherein the calculation formula for the quadrature pseudorandom noisede-spreading operation is:${I = {\frac{1}{\sqrt{2}}\left( {{I^{\prime}{PNI}^{\prime}} + {Q^{\prime}{PNQ}^{\prime}}} \right)}},{Q = {\frac{1}{\sqrt{2}}{\left( {{Q^{\prime}{PNI}^{\prime}} - {I^{\prime}{PNQ}^{\prime}}} \right).}}}$7. The method for de-spreading quadrature pseudorandom noise accordingto claim 1, wherein time-division multiplexing is performed on the datasequences I and Q with pilot and MAC information.
 8. The method forde-spreading quadrature pseudorandom noise according to claim 1, whereinthe pseudorandom noise sequences PN_(I) and PN_(Q) is adopted in thequadrature pseudorandom noise spreading performed on the data sequencesI and Q.
 9. The method for dc-spreading quadrature pseudorandom noiseaccording to any one of claims 1-6, 7-8 wherein the quadraturepseudorandom noise de-spreading method is applicable to EnhancedBroadcast MultiCast Service.
 10. A broadcast method for EnhancedBroadCast MultiCast Service, comprising: performing channel coding,channel scrambling, interleaving, repeating and punching, 16 QAM, OFDM,on data flow input from physical layer, and generating data sequences I′and Q′; performing quadrature pseudorandom noise de-spreading on thedata sequences I′ and Q′ by the method for de-spreading quadraturepseudorandom noise according to claim 1, and outputting data sequences Iand Q; and performing time-division multiplexing on the data sequences Iand Q with pilot and MAC information, adding base station informationthrough quadrature pseudorandom noise spreading, and transmittingbroadcast and multicast data thereby.